Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods and/or procedures disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein can be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments can apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description.
Long Term Evolution (LTE) is an umbrella term for so-called fourth-generation (4G) radio access technologies developed within the Third-Generation Partnership Project (3GPP) and initially standardized in Releases 8 and 9, also known as Evolved UTRAN (E-UTRAN). LTE is targeted at various licensed frequency bands, including the 700-MHz band in the United States. LTE is accompanied by improvements to non-radio aspects commonly referred to as System Architecture Evolution (SAE), which includes Evolved Packet Core (EPC) network. LTE continues to evolve through subsequent releases. One of the features of Release 11 is an enhanced Physical Downlink Control Channel (ePDCCH), which has the goals of increasing capacity and improving spatial reuse of control channel resources, improving inter-cell interference coordination (ICIC), and supporting antenna beamforming and/or transmit diversity for control channel.
The multiple access scheme for the LTE PHY is based on Orthogonal Frequency Division Multiplexing (OFDM) with a cyclic prefix (CP) in the downlink, and on Single-Carrier Frequency Division Multiple Access (SC-FDMA) with a cyclic prefix in the uplink. To support transmission in paired and unpaired spectrum, the LTE PHY supports both Frequency Division Duplexing (FDD) (including both full- and half-duplex operation) and Time Division Duplexing (TDD). FIG. 1 shows the radio frame structure used for FDD downlink (DL) operation. The radio frame has a fixed duration of 10 ms and consists of 20 slots, labeled 0 through 19, each with a fixed duration of 0.5 ms. A 1-ms subframe comprises two consecutive slots where subframe i consists of slots 2i and 2i+1. Each exemplary downlink slot consists of NDLsymb OFDM symbols, each of which is comprised of Nsc OFDM subcarriers. Exemplary values of NDLsymb can be 7 (with a normal CP) or 6 (with an extended-length CP) for subcarrier spacing (SCS) of 15 kHz. The value of Nsc is configurable based upon the available channel bandwidth. Since persons of ordinary skill in the art are familiar with the principles of OFDM, further details are omitted in this description. An exemplary uplink slot can be configured in similar manner as shown in FIG. 1, but comprises NULsymb OFDM symbols, each of which is comprised of Nsc OFDM subcarriers.
As shown in FIG. 1, a combination of a particular subcarrier in a particular symbol is known as a resource element (RE). Each RE is used to transmit a particular number of bits, depending on the type of modulation and/or bit-mapping constellation used for that RE. For example, some REs may carry two bits using QPSK modulation, while other REs may carry four or six bits using 16- or 64-QAM, respectively. The radio resources of the LTE PHY are also defined in terms of physical resource blocks (PRBs). A PRB spans NRBsc sub-carriers over the duration of a slot (i.e., NDLsymb symbols), where NRBsc is typically either 12 (with a 15-kHz SCS) or 24 (7.5-kHz SCS). A PRB spanning the same NRBsc subcarriers during an entire subframe (i.e., 2NDLsymb symbols) is known as a PRB pair. Accordingly, the resources available in a subframe of the LTE PHY downlink comprise NDLRB PRB pairs, each of which comprises 2NDLsymb•NRBscREs. For a normal CP and 15-KHz SCS, a PRB pair comprises 168 REs. The configuration of 15-kHz SCS and “normal” CP is often referred as the numerology, μ.
One exemplary characteristic of PRBs is that consecutively numbered PRBs (e.g., PRBi and PRBi+1) comprise consecutive blocks of subcarriers. For example, with a normal CP and 15-KHz sub-carrier bandwidth, PRB0 comprises sub-carrier 0 through 11 while PRB1 comprises sub-carries 12 through 23. The LTE PHY resource also can be defined in terms of virtual resource blocks (VRBs), which are the same size as PRBs but may be of either a localized or a distributed type. Localized VRBs can be mapped directly to PRBs such that VRB nVRB corresponds to PRB nPRB=nVRB. On the other hand, distributed VRBs can be mapped to non-consecutive PRBs according to various rules, as described in 3GPP Technical Specification (TS) 36.214 V15.0.0 or otherwise known to persons of ordinary skill in the art. However, the term “PRB” shall be used in this disclosure to refer to both physical and virtual resource blocks. Moreover, the term “PRB” will be used henceforth to refer to a resource block for the duration of a subframe, i.e., a PRB pair, unless otherwise specified.
As discussed above, the LTE PHY maps the various downlink and uplink physical channels to the resources shown in FIG. 1. For example, the PDCCH carries scheduling assignments, channel quality feedback (e.g., CSI) for the uplink channel, and other control information. Likewise, a Physical Uplink Control Channel (PUCCH) carries uplink control information such as scheduling requests, CSI for the downlink channel, hybrid ARQ feedback, and other control information. Both PDCCH and PUCCH are transmitted on aggregations of one or several consecutive control channel elements (CCEs), and a CCE is mapped to the physical resource shown in FIG. 1 based on resource element groups (REGs), each of which is comprised of a plurality of REs. For example, a CCE may be comprised of nine (9) REGs, each of which is comprised of four (4) REs.
While LTE was primarily designed for user-to-user communications, 5G (also referred to as “NR”) cellular networks are envisioned to support both high single-user data rates (e.g., 1 Gb/s) and large-scale, machine-to-machine communication involving short, bursty transmissions from many different devices that share the frequency bandwidth. The 5G radio standards (also referred to as “New Radio” or “NR”) are currently targeting a wide range of data services including eMBB (enhanced Mobile Broad Band) and URLLC (Ultra-Reliable Low Latency Communication). These services can have different requirements and objectives. For example, URLLC is intended to provide a data service with extremely strict error and latency requirements, e.g., error probabilities as low as 10−5 or lower and 1 ms (or less) end-to-end latency. For eMBB, the requirements on latency and error probability can be less stringent whereas the required supported peak rate and/or spectral efficiency can be higher.
In Release-15 (Rel-5) NR, a UE can be configured with up to four carrier bandwidth parts (BWPs) in the downlink (DL), with a single downlink carrier BWP being active at any given time. Likewise, a UE can be configured with up to four carrier BWPs in the uplink, with a single uplink carrier BWP being active at a given time. If a UE is configured with a supplementary uplink, the UE can also be configured with up to four supplementary carrier BWPs in the supplementary uplink with a single supplementary uplink BWP part being active at a given time.
In NR, a carrier BWP (e.g., an active BWP) can be configured with up to 275 RBs. Similar to LTE, an NR resource block (RB) (also referred to as “frequency-domain RB”) is defined as NscRB=12 consecutive subcarriers in the frequency domain. When scheduling a UE to receive PDSCH or transmit PUSCH, the network must allocate specific frequency-domain resources (i.e., RBs or RB groups, also referred to as RBGs) within the active BWP. As described above with respect to LTE, this allocation is performed using DCI sent via PDCCH. Due to strict limitations in DCI size, however, there can arise situations in which the number of bits available for signalling the resource allocation within the active BWP does not match the number of RBs in the active BWP. For example, the number of available bits can be insufficient to signal and/or indicate to the UEs all of the relevant combinations of RB allocations in the active BWP, including various starting positions and lengths. Accordingly, conventional approaches (e.g., as in LTE) for signalling frequency-domain resource assignments are inadequate.